Utilization of aluminum bronzes as a gold substitute has never become widespread in the ornamental and jewelry industry or in related products because of the difficulties of casting such bronzes due to the tendency of such alloys to cast into a generally woody grain structure.
Surface treatment of such castings has previously comprised mechanical abrasion since such prior art alloys are generally immune to chemical pickling or processing fluids.
With such alloys it has been difficult to solder or fuse the various fixtures thereto.
Prior art methods utilizing such aluminum bronzes have resorted to the inclusion of varying amounts of iron, nickel, silicon, manganese, tin, zinc, tellurium, lead and other materials in these alloys in order to render them capable of being readily cast. Substantial success has been achieved with castings using some of these metals and such castings using some of these metals and such castings as applied to machinery, where wear resistence and good corosion resistence is desired.
However, the use of an aluminum bronze containing aluminum and copper with the other metals mentioned has been unsuccessful for use as a substitute of gold in jewelry, artifacts and high detailed castings due to inferior results relating to the color complexion which is caused by the presence of the various foregoing metals added to the aluminum and copper.
These metals tend to reduce the color and luster characteristics as compared to the alloys containing only copper and aluminum. However, as heretofore set forth, such alloys of copper and aluminum alone are practically impossible to control as a casting material because of the pitting and woody grain structure at the surface of such castings.
While the addition of these various metals aforementioned make casting possible and help to eliminate the woody grain structure, the resultant alloys no longer have the rich appearance of gold but rather a dull, whitish-yellow which soon develops a dark coating as with the common bronzes.
Utilizing the foregoing prior art alloys, dirty looking castings are generally produced and brazing or soldering anything thereto is difficult. Additionally, polishing and buffing is very unsatisfactory and, therefore, castings of such material when an attempt is made to substitute for a gold color leaves a great deal to be desired.
A common and well-known prior art gold substitute has been Nurnberg gold, an alloy of 90% copper, 7.5% aluminum and 2.5% gold was invoked. This alloy was rendered relatively easy to cast by utilizing 2.5% gold; however, the usual salt tests on Nurnberg gold alloy was disappointing. This Nurnberg gold substitute produced a green-black coating within eight hours when subjected to a salt test.
Additionally, various articles of jewelry such as rings, and bracelets caused a green deposit on the skin of wearers which was highly undesirable.
Additionally, some of the foregoing aluminum bronzes containing lead or iron, for example, and containing some other of the foregoing mentioned materials would produce an alloy which could be used to make dark marks on paper and, consequently, articles made of such alloys tended to rub off even in a dry state on various articles adjacent thereto. Accordingly, costume jewelry and other devices made of such prior art alloys caused marking and discoloration of the skin as well as clothing or the like.